The former model and her husband, producer Scott Stuber, are expecting another baby together, she announced Tuesday on her website.

“I am BE-yond thrilled to share some very special news with you,” Sims, 41, writes.

“Scott, Brooks, and I are welcoming a fourth member to our little family — our second child!”

Along with the announcement, the mom-to-be posted a photo of herself and son Brooks Alan holding up chalkboards that read 4 months and 2 years.

“I can’t even being to explain just how excited we are for a new baby. We are so, so, so blessed as a family, and I’m speechless at the fact that we have the opportunity to bring a second bundle of joy into the world,” Sims writes.

“As a new mom to Brooks, an entire world of motherhood opened to me along with a thousand and one questions. I absolutely cannot wait to see what life will be like as a mother to a toddler and a newborn, and I really can’t wait to see Brooks as an older brother to Baby #2!”

The couple have yet to find out the sex of their baby, but Sims has high hopes that big brother Brooks will shine in his new role.

“I just know that he’s going to be preciously protective. If it’s a girl, he’ll be her biggest supporter and confident and if it’s a boy, I know they’ll be the best of friends, always getting into adventures together,” she shares.

“Scott, Brooks and I can’t wait to welcome Baby #2 to the Sims-Stuber household!!”

Earlier this month, Sims told PEOPLE she and Stuber were working on expanding their family.

“We’re starting to try for another one and it’s just so fun … you become a kid again!” she said.

The couple were engaged in May 2011 and tied the knot that September during an intimate ceremony in Napa Valley, California.